Various apparatus have been proposed for directing heated pressurized fluid streams, such as air or steam, into the surface of moving textile fabrics to alter the location of or modify the thermal properties of fibers or yarns therein and provide a pattern or visual surface change in such fabrics. Examples of such prior art equipment and methods of application of the pressurized fluid streams to a relatively moving material are disclosed in the following U.S. Pat. Nos.:
U.S. Pat. No. 2,110,118 PA1 U.S. Pat. No 2,241,222 PA1 U.S. Pat. No. 2,563,259 PA1 U.S. Pat. No. 3,010,179 PA1 U.S. Pat. No. 3,403,862 PA1 U.S. Pat. No. 3,434,188 PA1 U.S. Pat. No. 3,585,098 PA1 U.S. Pat. No. 3,613,186.
It is believed that such prior art treatment devices as described in the aforementioned patents, because of the nature of the equipment disclosed, are not capable of producing precise, intricate, or well defined patterns of wide variety in the fabrics, but generally can only produce limited, relatively grossly defined patterns, or surface modifications of a random, non-defined nature in the materials. In utilizing high temperature pressurized streams of fluid, such as air, to impart visual surface patterns to textile fabrics containing thermoplastic materials by thermal modification of the same, it can be appreciated that highly precise control of stream pressure, temperature, and direction is required in all of the individual heated streams striking the fabric to obtain uniformity and preciseness in the resultant pattern formed in the fabric. In addition, there are ever present difficulties in regulating the flow of high temperature fluid streams by use of conventional valving systems to selectively cut the stream flow on or off in accordance with pattern control information.
More recently, apparatus has been developed for more precisely and accurately controlling and directing high temperature streams of pressurized fluid, such as air, against the surface of a relatively moving substrate material, such as a textile fabric containing thermoplastic yarns, to impart intricate patterns and surface changes thereto. Such apparatus includes an elongate pressurized heated air distributing manifold having a narrow elongate air discharge slot extending across the path of fabric movement in close proximity to the fabric surface. Located within the manifold is a shim plate having a notched edge which resides in the discharge slot to form parallel spaced discharge channels through which the heated pressurized air passes in narrow, precisely defined streams to impinge upon the adjacent surface of the fabric. Flow of the individual heated air streams from the channels is controlled by the use of pressurized cool air which is directed by individual cool air supply tubes communicating with each channel to direct cool air into each discharge channel at a generally right angle to its discharge axis to block the passage of heated air therethrough. Each cool air tube is provided with an individual valve and the valves are selectively cut on and off in response to signal information from a pattern source, such as a computer program, to allow the heated air streams to strike the moving fabric in selected areas and impart a pattern thereto by thermal modification of the yarns.
To maintain more uniform temperature in the individual heated air streams along the full length of the distributing manifold, pressurized air is supplied to the distributing manifold through a bank of individual electric heaters which communicate with the manifold at uniformly spaced locations along its length and are regulated to introduce heated air at the desired temperature along the full length of the manifold.
Although such apparatus as described above provides for highly precise and intricate hot air patterning of substrate materials, in handling and distributing the high temperature air, a temperature drop occurs in the heated air during its passage through the manifold from the heater source to its point of discharge from the manifold. This temperature drop causes differential thermal expansion of the manifold housing which results in a displacement or bending of the manifold along its longitudinal axis. Such distortions become magnified in proportion to the length of the manifold, and present a serious problem when the distortions cause a variation in the distances of the manifold discharge outlets from the surface of the substrate material. If certain of the discharge outlets along the manifold are moved away from the substrate, the temperature, pressure, and preciseness of their streams striking the fabric will be reduced, resulting in a non-uniform patterning of the substrate across its width. Correspondingly, if certain of the manifold discharge outlets are moved closer to the substrate surface due to thermal distortion of the manifold, pattern variatins are again produced across the substrate. Additionally, the substrate may be damaged by overheating due to high temperature of the streams striking the substrate or by direct contact of the substrate with the hot manifold.